find strings in files

strings.hs

import Data.ByteString.Lazy.Char8 as BS
import Data.Word
import Data.Bits
import Data.List
import Data.Char
import Data.List.Split

isChar x = o > 31 && o < 127 where o = ord x

scan::[Char]->[Char]->[Char]

scan (x:xs) (y1:y2:y3:_) = if isChar x then [y1]++scan xs [y2,y3,x] else [y1,y2,y3,'\n']++scan xs []
scan (x:xs) (y1:y2:_) = if isChar x then scan xs [y1,y2,x] else scan xs []
scan (x:xs) (y1:_) = if isChar x then scan xs [y1,x] else scan xs []
scan (x:xs) [] = if isChar x then scan xs [x] else scan xs []
scan [] (y1:y2:y3:_) = [y1,y2,y3]
scan [] _ = []

main = do
    contents <- BS.readFile "inp"
    let foundStr = scan (unpack contents) []
    Prelude.writeFile "out.txt" foundStr